Interest on judgments.

Interest on judgments shall accrue as follows:

(1) Judgments founded on written contracts, providing for the payment of interest until paid at a specified rate, shall bear interest at the rate specified in the contracts: PROVIDED, That said interest rate is set forth in the judgment.

(2) All judgments for unpaid child support that have accrued under a superior court order or an order entered under the administrative procedure act shall bear interest at the rate of twelve percent.

(3)(a) Judgments founded on the tortious conduct of a "public agency" as defined in RCW 42.30.020 shall bear interest from the date of entry at two percentage points above the equivalent coupon issue yield, as published by the board of governors of the federal reserve system, of the average bill rate for twenty-six week treasury bills as determined at the first bill market auction conducted during the calendar month immediately preceding the date of entry. In any case where a court is directed on review to enter judgment on a verdict or in any case where a judgment entered on a verdict is wholly or partly affirmed on review, interest on the judgment or on that portion of the judgment affirmed shall date back to and shall accrue from the date the verdict was rendered.

(b) Except as provided in (a) of this subsection, judgments founded on the tortious conduct of individuals or other entities, whether acting in their personal or representative capacities, shall bear interest from the date of entry at two percentage points above the prime rate, as published by the board of governors of the federal reserve system on the first business day of the calendar month immediately preceding the date of entry. In any case where a court is directed on review to enter judgment on a verdict or in any case where a judgment entered on a verdict is wholly or partly affirmed on review, interest on the judgment or on that portion of the judgment affirmed shall date back to and shall accrue from the date the verdict was rendered.

(4) Except as provided under subsection (1) of this section, judgments for unpaid private student loan debt, as defined in RCW 6.01.060, shall bear interest from the date of entry at two percentage points above the prime rate, as published by the board of governors of the federal reserve system on the first business day of the calendar month immediately preceding the date of entry.

(5) Except as provided under subsection (1) of this section, judgments for unpaid consumer debt, as defined in RCW 6.01.060, shall bear interest from the date of entry at a rate of nine percent.

(6) Except as provided under subsections (1) through (5) of this section, judgments shall bear interest from the date of entry at the maximum rate permitted under RCW 19.52.020 on the date of entry thereof. In any case where a court is directed on review to enter judgment on a verdict or in any case where a judgment entered on a verdict is wholly or partly affirmed on review, interest on the judgment or on that portion of the judgment affirmed shall date back to and shall accrue from the date the verdict was rendered. The method for determining an interest rate prescribed by this subsection is also the method for determining the "rate applicable to civil judgments" for purposes of RCW 10.82.090.